Add PaymentFailureReason::InvoiceRequestRejected

Instead of re-using PaymentFailureReason::RecipientRejected, define a
new InvoiceRequestRejected variant for when an InvoiceError is received
instead of a Bolt12Invoice. This allows user to differentiate the cause
of the failure.

Author: jkczyz

lightning/src/events/mod.rs

@@ -501,7 +501,7 @@ impl_writeable_tlv_based_enum!(InterceptNextHop,
 /// The reason the payment failed. Used in [`Event::PaymentFailed`].
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum PaymentFailureReason {
-	/// The intended recipient rejected our payment or invoice request.
+	/// The intended recipient rejected our payment.
 	RecipientRejected,
 	/// The user chose to abandon this payment by calling [`ChannelManager::abandon_payment`].
 	///
@@ -532,6 +532,10 @@ pub enum PaymentFailureReason {
 	UnknownRequiredFeatures,
 	/// A [`Bolt12Invoice`] was not received in a reasonable amount of time.
 	InvoiceRequestExpired,
+	/// An [`InvoiceRequest`] for the payment was rejected by the recipient.
+	///
+	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
+	InvoiceRequestRejected,
 }
 
 impl_writeable_tlv_based_enum!(PaymentFailureReason,
@@ -540,6 +544,7 @@ impl_writeable_tlv_based_enum!(PaymentFailureReason,
 	(2, UserAbandoned) => {},
 	(3, InvoiceRequestExpired) => {},
 	(4, RetriesExhausted) => {},
+	(5, InvoiceRequestRejected) => {},
 	(6, PaymentExpired) => {},
 	(8, RouteNotFound) => {},
 	(10, UnexpectedError) => {},

lightning/src/ln/channelmanager.rs

@@ -10897,7 +10897,7 @@ where
 					Some(OffersContext::OutboundPayment { payment_id, nonce, hmac: Some(hmac) }) => {
 						if signer::verify_payment_id(payment_id, hmac, nonce, expanded_key) {
 							self.abandon_payment_with_reason(
-								payment_id, PaymentFailureReason::RecipientRejected,
+								payment_id, PaymentFailureReason::InvoiceRequestRejected,
 							);
 						}
 					},

lightning/src/ln/offers_tests.rs

@@ -1932,8 +1932,9 @@ fn fails_sending_invoice_without_blinded_payment_paths_for_offer() {
 
 	// Confirm that david drops this failed payment from his pending outbound payments.
 	match get_event!(david, Event::PaymentFailed) {
-		Event::PaymentFailed { payment_id: actual_payment_id, .. } => {
+		Event::PaymentFailed { payment_id: actual_payment_id, reason, .. } => {
 			assert_eq!(payment_id, actual_payment_id);
+			assert_eq!(reason, Some(PaymentFailureReason::InvoiceRequestRejected));
 		},
 		_ => panic!("No Event::PaymentFailed"),
 	}